How do Plan Species Invasions Affect Water Quality Services Performed by Great Lakes Coastal Wetlands?

Final Report

To determine how plant species invasions influence the biogeochemical capacity of Illinois/Indiana Great Lakes coastal wetlands to remove nitrogen through denitrification, to provide science-based recommendations to managers challenged with maintaining the ecological integrity of Illinois/Indiana Great Lakes coastal wetlands, and to help them prioritize efforts to manage invaded wetlands, we propose to:

  • Objective 1: Characterize the relationships between invasive species and water quality ecosystem services in Illinois and Indiana coastal wetlands. 1a: Determine effects of invasive species cover (Typha x glauca and Phragmites australis) on denitrification rates. 1b: Determine if high cover of invasive species promotes terrestrialization (increased elevation, reduced soil moisture and redox potential) and if such abiotic changes reduce denitrification.
  • Objective 2: Develop site-specific management recommendations for optimizing ecosystem services based on improved understanding of invasive species effects on denitrification.
  • Objective 3: Provide educational and research opportunities for graduate and undergraduate students centered on improving the scientific basis for stewardship of IL-IN coastal wetlands.

At four coastal wetland sites on the IL-IN shoreline of Lake Michigan, we will characterize the relationships between invasive species and water quality ecosystem services. We will measure plant cover (invasive and native species), soil nutrient concentrations (nitrate, ammonium, and organic carbon), soil organic matter, soil moisture content, soil redox potential, and denitrification potential (using the acetylene inhibition technique)(Groffman et al. 1999). To determine if high cover of invasive species promotes terrestrialization, we will use survey-grade, high-precision GPS instrumentation to measure topographic elevation within stands of native and invasive vegetation. If there are significant correlations between invasive species dominance and fine-scale elevation changes, we will address whether invaders altered elevation or if invasion was itself elevation-dependent. We will use field survey data and interpretation of historic and current aerial photos to identify approximate ages of discrete stands of Typha and Phragmites in our least disturbed site (Spring Bluff Nature Preserve). We will select paired stands of native vegetation and invasive species approximately-aged through interpretation of aerial photo time sequences (as employed in Boers 2005). From these locations, we will collect sediment core samples, section them by depth, analyze their ratio of organic matter to mineral content, and submit subsamples for isotopic lead (lead-210) dating to age sediment depth profiles and calculate rates of sediment accretion. Ratios of organic to mineral matter will elucidate whether the mechanism of terrestrialization occurs via litter inputs or via enhanced capture of sediments from Lake Michigan or upland sources. To develop management recommendations for optimizing the ecosystem services these wetlands provide, we developed a survey intended for managers of the several wetlands that are part of this study. The survey aims to capture the needs for basic scientific research these managers have in order to effectively implement management practices when faced with invasive species. Once returned, we will compile the information from the survey and develop site-specific management recommendations based on our results from Objective 1. During our work we will collaborate with site managers to ensure the "real-world" applicability of our research. Upon completion of our research, we will present our findings and recommendations to wetland managers. To provide educational and research opportunities in ecological research, we will train a graduate student and several undergraduates in the Department of Biology at Loyola University Chicago. Their experiences will involve literature familiarization through weekly lab meetings, experimental design, field work, processing and analyzing samples, data interpretation, and presentation of results. Students will be strongly encouraged to participate in local symposia, where they will present posters on their research and gain valuable feedback from faculty and other students. We will bring students to national meetings, and will include them as co-authors on peer-reviewed publications arising from the project.

It is often implied that wetlands can "do it all", i.e., have high biodiversity while guarding communities against flooding and enhancing water quality. However, some functions may be mutually incompatible or not achievable in certain wetlands. It is critical to identify what functions are salvageable in already-invaded wetlands unlikely to support diverse native flora in the near term. In urban Great Lakes coastal watersheds, N removal through denitrification is a valuable ecosystem service known to be impacted by vegetation composition. However, the nature of the relationship between invasive species dominance and denitrification is not well understood. Developing this understanding in a way that informs wetland management is critical to optimizing the value of IL-IN coastal wetlands. Our objectives are strongly aligned with IL-IN Sea Grant priority research areas related to aquatic invasive species, habitat restoration, watersheds, ensuring future water quality, and supporting the sustainability of coastal cities. Specifically, the proposed research would 1) improve understanding of how key ecosystem functions performed by IL-IN coastal watersheds are impacted by invasive species, 2) contribute to improved prioritization for habitat restoration efforts, and 3) enhance understanding of water quality services provided by coastal wetlands that support the sustainability of IL-IN coastal cities. In addition, the proposed research is aligned with IL-IN Sea Grant goals to provide training opportunities for graduate and undergraduate students through participation in research.

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Research Information

  • Principal Investigator: Nancy Tuchman
  • Initiation Date: February 1, 2008
  • Completion Date:January 31, 2010
  • Affiliation: Loyola University Chicago


Tomas Höök

Associate Director of Research

Carolyn Foley
Assistant Research Coordinator

Pat Charlebois
Aquatic Invasive Species Coordinator


Sarah Zack
Aquatic Invasive Species Specialist

Danielle Hilbrich
Aquatic Invasive Species Assistant

Illinois-Indiana Sea Grant
Purdue University
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West Lafayette, IN 47907-2033
University of Illinois Extensio
Sea Grant
Purdue University